Electric discharge apparatus



March 15, 932. a. F MURPHY ELECTRIC DISCHARGE APPARATUS Filed June 27, 1

Will-Ill nventor 26 T. murph l l/LM His Attorne Patented Mar. 15, 1932UNITED STATES PATENT OFFICE GEORGE E. MURPHY, OF SCHENECTADY, NEW YORK,ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRICDISCHARGE APPARATUS Application filed June 27,

The present invention relates to electric discharge apparatus and moreparticularly to power tubes which employ electrodes of considerablesize.

While in the manufacture of all kinds of radio tubes it is desirable tospace the elec- 4 trodes accurately at predetermined distances apart inorder to obtain the proper operating characteristics, this requlrement1s absolutely imperative in power tube construction. In tubes of largersize, i. e. transmitting amplifiers, oscillators, modulators or thellke, the electrodes, particularly the grid and anode are often veryclosely spaced and in view of the considerable extent of the surfaceswhich may parallel one another at this close spacing, also in view ofthe considerable electrostatic mutual attraction between the surfaces athigh operating potentials, it is necessaryto maintain the position ofthe electrodes rigidly with respect to one another in the assembly, andto provide an exceptional degree of ruggedness of electrode constructionas well as an effective support at the place where the assembly isattached to the envelope. The last mentioned requirement, i. e. therigid support between the electrodes and the envelope, heretofore hasbeen satisfactorily met by the employment of two oppositely directedreentrant stems between which the electrodes are positioned by collarsembracing the stems, secured thereto by clamps. However, it has beenfound that notwithstanding the rigidity offered by the stem and collararrangement referred to, the operating characteristics of each tube madein quantity production are not always strictly alike according topredetermined required values and there have also been cases of tubefailure during operation. These results have been attributed to the factthat there may have been a distortion or twist of the electrode assemblywhen the elements were aligned and fitted between the stems, whichirregularities of construction were accentuated at the elevatedtemperatures to which the tubes are subjected during operation or elsethe electrode structure was such as to lend itself to warping underheated conditions, or both. I have found that when the electrodes andtheir 1929. Serial No. 374,132.

supports are fabricated in the manner described hereinafter, not onlywill the operating characteristics of the various tubes of 7 similartype be substantially alike but also tube failure may be reduced in alarge degree.

Accordingly, one of the objects of my inventlon is to improve theelectrode structure of power tube apparatus whereby the tube giveslonger operating life than devices heretofore constructed, the improvedconstruction to be characterized by being reproducible on a quantityproduction basis and to endow the devices made in the imp oved mannerwith similar predetermined opgrating characteristics per tube. Thisobject is attained in brief by providing an improved form of anode, alsoan improved arrangement for supporting the anode and grid within theelectrode assembly. Other objects and features will be apparent as thespecification is perused in connection with the accompanying drawings inwhich Fig. l is an elevational view of a tube and electrodes improved inaccordance with my invention while Fig. 2 is an elevational view inperspective of the electrode assembly secured in place between thereentrant stems of an envelope (not shown in this figure).

In the drawings, numeral 1 designates an evacuated envelope terminatingat opposite ends in reentrant stems 2, 3. The electrode assembly issupported between these stems by means of collars 4, 5 and clamp rings6. There is secured a fiat member 7 preferably of lava or steatite firedin hydrogen to the collar 4. The latter is closed at its lower end, asshown, by a metal plug 30 which is spot welded or otherwise secured tothe collar. The plug is counter-bored to reduce the amount of containedmetal and is provided with a pair of tapped holes which receive twoscrews 31 for securing the member 7 to the collar. I11 accordance withmy invention the collar 5 is provided with a metal flange member 8 whichhas oppositely extending portions 9, 10 containing two pairs of holesthrough which are threaded two pairs of parallelly extending uprights orstay rods 11, 11 which may be riveted to the flange member at the underside. The other ends of the rods are I loosely threaded through suitablspaced openings in the member 7. A gri 12 00111- posed of wire mesh iswound about the rods 11 and secured-thereto in any suitable manner, e.g. by spot welding or bound with wire. There is an M-shaped filament(not shown) within the grid having its upper apices secured to anchorwires 13, 13 which are mounted under tension by means of a pair ofcompression springs 14, 14. These springs are fitted at each end withcaps 15, the anchor wires being rigidly connected to the upper caps. Thecaps are seated on a lava member 16 which is rigidly secured to the gridstay wires 11, and above this member is another lava piece 17 separatedfrom the member 16 by spacing collars 18, serving to limit the upwardmovement of the compression springs. The lower ends of the filament asshown terminate in tic wires 19 and lead-in conductors 2O fused in thestem. According to another feature of my invention the anode takes theform of a hollow perimetrically complete body 21 preferably ofmolybdenum and fabricated in four sections, the two outer sections 21,21 having square ends and provided with normally extending flanges 22,22. The inner sections 23, 23 are straight for the major portion andalso terminate in flanges which are bent to conform to those of theouter sections to which they are secured by riveting. Extendinghorizontally across the entire width of the anode there are severalrigidly secured channel bars 2-l to strengthen the anode; the uprightflange members 22, 22

are provided with openings to receive these bars in the manner shown.The anode thus has a strictly rectangular cross section because it isfound that the square end construction not only offers advantage overthe prior art semicircular ended type by way of greater ease ofmanufacture but also lends considerable strength to the structure. Inbeing arranged normal to the sides of the anode the metal of the endsoffers a greater compressional resistance to deformation or warp of theanode as a whole than in the case of the semicircular end. Moreover, byproviding a member of rectangular cross section, it is possible toextend the laterally positioned bars to the extreme width of the memberthereby providing additional ruggedness to the sides of this electrode.The use of channels as strengthening members is decidedly advantageousin providing the greatest amount of strength for the minimum amount ofmaterial involved, also in offering the greatest amount of surface forradiating heat, thus causing the entire surface of the anode to run at avery even temperature. The anode is supported at the upper end asillustrated by four stay rods 25 secured to the anode at the flanges 22;the rods fit tightly in small openings boredthrough the plug 30 ofcollar 4 and are anchored thereto preferably by spot welding. The otherend of the anode likewise is supported by stay rods 26 attached to theflanges 22 and extending parallelly downward or rectilinear with respectto the anode to a plaje member 27, preferably of lava which fixes thelateral spacing of these rods. This plate member is provided withprojections 28 in which suitably spaced holes are drilled to receive thegrid uprights 11 and also the rods 26, the lava member being fixed tothe uprights 11. The rods 26 pass through the holes with a sliding fitin order to accommodate the longitudinal expansion of the anode. It willbe noted that the eifective width of the member 27 is such as to allowthe rods 26 to extend directly downward from the flanges 22 withoutnecessitating a bend inwardly as is present in the prior constructionson account of the narrowness of this lava piece in the prior art tubes.Hence, the improved shape of the lava member 27 provides the maximumamount of support to the anode from a torsional standpoint w-hileaccommodating the longitudinal expansion of the latter and of the anodestay rods during operation. Moreover, it is apparent that by increasingthe width of the member 27 over the prior constructlons, the leakagedistance between the grid stay wires 11 and the anode rods 26 isincreased accordingly. It will also be apparent that the flange member 8to which the grid stay wires are riveted rigidly fixes these wires inplace and together with lava mem bers 7 and 27 positively precludesdisplacement of the grid with respect to the anode structure by twist orother distortional stress. It has been found that an anode unitconstructed in the manner set forth hereinbefore and temporarilyassembled before the collars were placed over the stems 4c, 5constitutes a rigid body as a whole and positively precludes torsionalstrain or other displacement of the various electrodes with respect toone another. Hence, a construction of this sort is particularlydesirable in the cases Where electrodes are of large area and thespacing therebetween is close and critical. This unusual degree ofruggedness and rigidity of the electrode assembly is enhanced by thefact that the electrode unit is securely attached to the reentrant stems2,3 which form part of the envelope.

If desired, and as shown in Fig. 2, a capsule 29 containing gettermaterial for the well understood purpose may be attached to theprojection 9; the capsule feature, however, does not constitutea part ofmy invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. In an electric discharge device, an evacuated envelope terminating inoppositely directed stems, an electrode assembly arranged between thestems, said assembly including a grid and an anode, means for rigidlypositioning the grid in place, said means comprising a flange membersecured to one of the stems, stay rods aflixed at one end to said memherfor supporting the grid and at the other end to a plate member securedto the other of said stems, means for rigidly supporting the anode fromthe stem to which said plate member is attached, the opposite end of theanode being provided with rods, a second plate member positioned betweensaid flange memberand the grid, said second plate member being securedto the stay rods and adapted to receive the anode rods whereby theelectrode assembly constitutes a rigid unit and distortion by twist isprecluded. Y 2. In an electric discharge device, an evacuated envelopeterminating in oppositely directed stems, an electrode assembly arrangedbetween the stems, said assembly including an anode'of rectangular crosssection and a grid, said anode constituting closely spaced surfaces ofrelatively large area, means for rigidly positioning the grid in place,said means comprising a flange member secured to one of the stems, stayrods aflixed at one end to said member for supporting the grid and atthe other end to a plate member secured to the other of said stems,means for rigidl supporting the anode from the stem to whic said platemember is attached, the opposite end of the anode being provided withrods, a second plate member positioned between said flange member andthe grid, said second plate member being secured to the grid stay rodsand adapted to receive the anode rods whereby the electrode assemblyconstitutes a rigid unit and the spacing between the electrodes isstrictly maintaine under operating conditions.

3. In an electric discharge device, an evacu- 40 ated envelopeterminating in oppositely directed stems, an electrode assem 1y arrangedbetween the stems, said assembly including a grid and an anode, meansfor rigidly positioning the grid in place, said means comprising aflange mem er secured to one of the stems, stay rods ailixed at one endto said mem her for supporting the grid and at the other end to a platemember securedto theother of said stems, means for rigidly supportingthe anode from the stem to which said late member is attached, theopposite end 0 the anode being *rovided with rods, a second plate memberpositioned between said flange member and the grid, said second platememher being secured to the grid stay rods and adapted to receive theanode rods whereby the electrode assembly constitutes a rigid unit anddistortion by twist is recliided. In witness whereof, have hereunto setmy hand this 26th day of June, 1929.

GEORGE F. MURPHY.

